1. Field of the Invention
The present invention relates to a printer with sheet front loader.
2. Description of the Prior Art
Low cost fast printers for data processing systems are available on the market. According to the most recent trends such printers may use both continuous form feeding with lateral perforations and discrete sheets. For these type printers a problem exists in loading the equipment with discrete single sheets by means of simple and fast operations and low cost devices. An example of a method for loading printers with individual sheets is the one used in typewriters. It consists of inserting a sheet between a feed roll, which also acts as a platen, and pressure rollers. An operation then follows which puts the pressure rollers near the feed roll in order that the sheet can be gripped between the feed roll and pressure rollers, which is further followed by an operation for manually moving the feed roll by knobs so as to bring the desired sheet in the desired position. This process requires a reatively long time.
Automatic sheet feeding devices are also used which perform a top feeding of the sheet. In other words, the sheet is inserted from the top in a suitable housing and some feeding rolls automatically lead the sheet downwards and provide for its advance, in an opposite direction when the printing of each of the several rows is performed. Suitable sensors generate signals according to the position of the sheet and control the feeding rollers. A feeding device of this type is disclosed in European Pat. No. 0024662. These feeding devices, though efficacious are relatively expensive and require a bidirection control of the feeding rolls.
The "front end" loading devices for single sheets, recently put on the market, overcome such disadvantages. These devices have a plate which acts as a frontally open chute where the sheets can be inserted. The back part of the chute is bent upwards acting as a guide which leads the sheet towards the feeding roller and facilitates its insertion between feeding roll and pressure rollers. When the sheet contacts the feeding roll, sensors are activated which start the feeding roll movement. The feeding roll then provides a suitable advance of the sheet upwards. A feeding device of this type is disclosed by U.S. Pat. No. 4,302,116. This kind of device is particularly simple, efficacious and inexpensive, but it is cumbersome because of the chute which must have a frontally receiving throat wide enough to allow easy handling of the sheet. Lacking such throat it is necessary to use sheets having a length adequate for the chute length. In fact, when the sheets are positioned into the chute and the upper edge of a sheet contacts the feeding roll, it is necessary for the back edge of the sheet to be accessed from the outside in order to allow the manual manipulation of the sheet towards the inside of the chute. Such restriction can be reduced by cutting to a minimum the distance between the frontal opening of the chute and the line where the sheet will contact the feeding roll. This can be obtained by keeping to a minimum the horizontal and vertical paths of the chute; that is, the printer body has to be ideally divided in forward/upper position containing only the printing devices and a back/lower portion, the two portions being separated by the chute, thus causing evident construction complications. With this type of device standard size sheets ISO A4 (21.times.29.7 cm) or of corresponding standard size sheets used in the U.S.A. (21.6.times.28 cm) can be used and fed in the direction of their greater dimension. However the printer size and the corresponding length of the chute prevent the feeding of the sheets in the direction of the sheet width. In other words, though the printers available on the market are able to print on a sheet having a width of more than 30 cm. a correct insertion in the chute of the sheets in the direction of their smaller dimension cannot be made. It is desirable, therefore, to print on discrete sheets of standard size which can be fed with either dimension.